Dissertation

Engineered Ferrite Superstrate Based Scan Characteristics of Fabry-Perot Cavity Antenna

Sultan, Farooq

2015

Overview

In radars and wireless communication devices, phased array antennas are widely used to steer the direction of the main beam. Typically, array of radiating patches with progressively phased excitation are used to realize beam scan, resulting in complex antenna structures. In this dissertation, two different techniques to scan the main beam of a Fabry-Perot cavity (FPC) antenna without using phased excitation signals are presented. These alternative scanning mechanisms use a multilayered dielectric-ferrite superstrate to control the E-field distribution of the radiation path. Low-loss operating regions of the ferrite rods are analytically identified from the characteristic equation and are used in the simulations and measurements. Using the first technique, a single 10 GHz microstrip patch antenna (MPA) is loaded with a foam-ferrite superstrate to demonstrate a measured beam scan of ±30° for a differential biasing field of H0=0.1875 T. By integrating an additional dielectric layer, the resulting FPC excited with an MPA shows a 1.4 dB increase in directivity at the cost of reduced scanning angle. To optimize the design, the FPC antenna with multilayer superstrate is excited with a thinned 2-patch linear array. The foam-ferrite layer of the superstrate, now with three axially magnetized ferrite rods, is optimized to control Ey-phase taper needed for the beam scan. By individually biasing the ferrite rods, the main beam of the structure is scanned up to ±12° for a differential magnetization field of 0.182T (H0=150 kA/m). This method also reduces the side lobe level by 3.56 dB for maximum scan angle; which is important as typical FPC antenna demonstrates an increase in side lobe level with increasing scan angle. The second technique involves integrating the ferrite superstrate with split-ring resonators (SRR) to decrease the biasing field requirements. Two different configurations, with one or two SRR integrated ferrite rods, are designed and simulated. The resulting structures demonstrate equivalent beam scans at significantly lower biasing fields with reduced cavity heights as well. Although the presented designs are not low-profile, use of low temperature co-fired ceramics (LTCC) can reduce the cavity heights and also help incorporating the biasing coils within the ferrite rods.

• Publisher: ProQuest Dissertations & Theses
• Subject: Electrical engineering / Electromagnetics
• ISBN: 9798374415674